Light emitting device

ABSTRACT

A light emitting device includes a wiring substrate, light emitting elements, light-reflecting films, and a light diffusing member. The light emitting elements are mounted in a matrix on the wiring substrate. Each of the light emitting elements includes a sapphire substrate having a lower surface, first lateral surfaces inclined to the lower surface, and second lateral surfaces perpendicular to the lower surface, and a semiconductor layered structure disposed on the lower surface. The light-reflecting films are respectively disposed on the light emitting elements. The light diffusing member is disposed above the light emitting elements. At least a group of the light emitting elements is arranged such that, in every adjacent ones of the light emitting elements in at least one of a row direction and a column direction, the first lateral surface of the light emitting element faces the second lateral surface of the adjacent light emitting element.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to Japanese Patent Application No.2017-250606 filed on Dec. 27, 2017, and Japanese Patent Application No.2018-232286 filed on Dec. 12, 2018. The entire disclosures of JapanesePatent Application No. 2017-250606 and Japanese Patent Application No.2018-232286 are hereby incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to a light emitting device.

Description of Related Art

When a plurality of LED elements of the same structure are arrangedregularly in the same orientation in a conventional LED array panel andthe luminous intensity distributions of the light emitted from the LEDelements exhibit a certain pattern, the certain pattern of light fromthe plurality of LED elements may be overlapped when condensed,resulting in uneven illuminance which may further resulting inprojecting an image on a screen.

In order to obtain a uniform luminous intensity distribution on theirradiated surface, the plurality of light emitting elements in the LEDarray panel may be arranged at angles different by 90° around theoptical axis, such that light emitted from the light emitting elementswith luminous intensity distribution exhibiting a certain pattern isoverlapped to produce a uniform luminous intensity distribution, whichis, for example, proposed in Japanese Unexamined Patent ApplicationPublication No. 2002-374004.

SUMMARY OF THE INVENTION

Meanwhile, in a direct-type or direct-lit backlight light source, aplurality of light emitting elements are generally arranged in the sameorientation in a matrix of rows and columns at a uniform pitch. In sucha configuration, when unevenness in luminance occurs around a singlelight emitting element, the same or similar unevenness in luminancewould successively continue in the rows or the columns, which may bevisually recognized on the light-emitting surface of the backlight lightsource. Such a visually recognizable unevenness in luminance on thelight-emitting surface of the backlight light source tends to beinherited on the irradiated surface of a liquid crystal panel etc.

Accordingly, an aim of the present disclosure is to provide a lightemitting device in which a plurality of light emitting elements having aspecific three-dimensional shape and specific light distributioncharacteristics are arranged in a matrix of rows and columns at auniform pitch, successively continuing unevenness in luminance alongrows and/or columns is not or hardly visually recognized on the lightemitting surface and/or on the irradiated surface.

The embodiments include the aspects described below.

A light emitting device includes a wiring substrate, a plurality oflight emitting elements, a plurality of light-reflecting films, and alight diffusing member. The wiring substrate has light-reflectingproperties. The wiring substrate includes a wiring. The light emittingelements are mounted in a matrix of rows and columns on an upper surfaceof the wiring substrate. Each of the light emitting elements includes asapphire substrate having a lower surface, a pair of first lateralsurfaces inclined to the lower surface, and a pair of second lateralsurfaces perpendicular to the lower surface, and a semiconductor layeredstructure disposed on the lower surface of the sapphire substrate. Thelight-reflecting films are respectively disposed on upper surfaces ofthe light emitting elements. The light diffusing member is disposedabove the light emitting elements. At least a group of the lightemitting elements disposed in a predetermined region is arranged suchthat, in every adjacent ones of the light emitting elements in at leastone of a row direction and a column direction of the matrix, one of thepair of first lateral surfaces of one of the light emitting elementsfaces one of the pair of second lateral surfaces of an adjacent one ofthe light emitting elements.

According to the present disclosure, a light emitting device having aplurality of light emitting elements of certain structure and certainlight distribution characteristics arranged in a matrix of rows andcolumns with a number of rows and a number of columns at a uniformpitch, visual recognition of unevenness in luminance along rows and/orcolumns can be effectively prevented or reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic plan view showing a light emitting deviceaccording to one embodiment.

FIG. 1B is an enlarged schematic plan view illustrating an arrangementof light emitting elements in a region M in FIG. 1A.

FIG. 1C is a schematic cross-sectional view taken along line A-A′ ofFIG. 1B.

FIG. 2A is a graph showing light-transmissive characteristics of alight-reflecting film.

FIG. 2B is a graph showing light distribution characteristics of a lightemitting element 12T, in X-direction of FIG. 1B.

FIG. 2C is a graph showing light distribution characteristics of thelight emitting element 12T, in a direction perpendicular to X-directionof FIG. 1B.

FIG. 3 is a schematic plan view illustrating an arrangement of lightemitting elements in the region M of a light emitting device accordingto another embodiment.

FIG. 4 is a schematic plan view illustrating an arrangement of lightemitting elements in the region M of a light emitting device accordingto yet another embodiment.

FIG. 5 is a schematic plan view illustrating an arrangement of lightemitting elements in the region M of a light emitting device accordingto yet another embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments shown below are intended as illustrative to give aconcrete form to technical ideas of the present invention, and the scopeof the invention is not limited to those described below. The sizes andthe positional relationships of the members in each of the drawings areoccasionally shown exaggerated for ease of explanation. Further, in thedescription below, the same designations or the same reference numeralsdenote the same or like members and duplicative descriptions will beappropriately omitted.

Light Emitting Device

As shown in FIG. 1A, a light emitting device 10 according to oneembodiment of the present invention includes a plurality of lightemitting elements 12 arranged in a matrix of rows and columns on anupper surface of a wiring substrate 11. In the light emitting device 10,as shown in FIG. 1B and FIG. 1C, the wiring substrate 11 includes awiring 11 a on a substrate 11 b and the wiring substrate 11 haslight-reflecting properties. A light-reflecting film 13 is disposed onan upper surface of each of the light emitting elements 12, and a lightdiffusing member 14 is disposed above the plurality of light emittingelements 12. Each of the light emitting elements 12 includes a sapphiresubstrate 21 and a semiconductor layered structure 22. The sapphiresubstrate 21 has a lower surface 21 c, a pair of first lateral surfaces21 a inclined to the lower surface 21 c, and a pair of second lateralsurfaces 21 b perpendicular to the lower surface 21 c. A part of theplurality of light emitting elements 12 disposed in a predeterminedregion, for example, a region M in FIG. 1, are arranged such that one ofthe pair of first lateral surfaces 21 a of one of the light emittingelements 12 faces one of the pair of second lateral surfaces 21 b of anadjacent one of the light emitting elements 12 among the plurality oflight emitting elements 12 in at least one of a row direction and acolumn direction. In the present specification, the expressions “onesurface faces another surface” and “two surfaces face each other” referto a state in which the two surfaces are generally facing toward eachother, and is not limited to a state in which the two surfaces areprecisely in parallel to each other. More specifically, the expressions“one surface faces another surface” and “two surfaces face each other”include a state in which one of the facing surfaces is inclined to theother of the facing surfaces, for example, as shown in FIG. 4.

The direction of light emitted from a light emitting element is affectedby the pair of first lateral surfaces inclined due to a cleavage planeof the sapphire substrate, but with the configuration as describedabove, the directions of light emitted from the light emitting elementscan be set in different directions between adjacent light emittingelements arranged in the row direction or in the column direction.Accordingly, successively continuing brighter pattern and successivelycontinuing darker pattern that occur when arranging regularly and in thesame orientation a plurality of light emitting elements each having arelatively brighter side and a relatively darker side when viewed fromabove can be effectively avoided. Accordingly, in the light emittingdevice, uniform intensity distribution of light can be obtained on thelight emitting surface and visual recognition of unevenness in theluminance can be avoided. Such effects can be more significantlyachieved by providing a light-reflecting film on the upper surface ofeach of the light emitting elements, in applications in which a greatnumber of light emitting elements each substantially does not allowlight to pass through in a direction perpendicular to the upper surfaceare disposed, particularly in an application for direct-type backlightlight source.

Wiring Substrate 11

The wiring substrate 11 has at least one surface (for example an uppersurface) provided with a wiring 11 a. The wiring 11 a includes aplurality of pairs of patterns each corresponding to positive andnegative electrodes of the light emitting elements. The pairs ofpatterns each corresponding to positive and negative electrodes arerespectively electrically connected to a first surface, inside and/or asecond surface opposite to the first surface (for example, a lowersurface) of the wiring substrate 11 to supply electric current (electricpower) from the outside.

Wiring 11 a

The material of the wiring 11 a can be appropriately selected based onthe material of the substrate 11 b, a method of manufacturing, or thelike. For example, when ceramics is used for the material of thesubstrate 11 b, the wiring 11 a is preferably made of a material havinga high melting point durable at a calcination temperature of ceramicssheet, examples thereof include a high-melting point metal such astungsten, molybdenum, or the like. The substrate 11 b may further becoated with a metal material such as nickel, gold, silver, or the likeby way of plating, sputtering, or vapor deposition.

When a resin material such as a glass-epoxy resin is used for thesubstrate 11 b, the wiring 11 a is preferably made of a material that iseasily processed. The wiring 11 a can be formed on an upper surfaceor/and a lower surface of the substrate 11 b by plating, vapordeposition, sputtering, printing, coating, or the like. Alternatively,for the wiring 11 a, a thin metal film may be attached by pressing, orpattern of predetermined shape may be formed by applying a mask by wayof printing, photolithography, or the like, and then performing etching.For example, a metal such as copper, silver, gold, or nickel, or analloy of those may be used.

Substrate 11 b

The substrate 11 b can be made of; for example, ceramics, a resinmaterial such as a glass-epoxy resin, a phenol resin, an epoxy resin, apolyimide resin, a BT resin, a polyphthalamide (PPA), or polyethyleneterephthalate (PET), or a metal.

The substrate 11 b can have an appropriate thickness.

Examples of the ceramics include alumina, mullite, forsterite,glass-ceramics, nitride-based (for example, AlN) ceramics, carbon-based(for example, SiC) ceramics, and low temperature co-fired ceramics(LTCC).

When a resin material is used, an inorganic filler such as glass-fiber,SiO₂, TiO₂, Al₂O₃ or the like may be mixed in a resin material toimprove in mechanical strength, to decrease in thermal expansioncoefficient, to improve optical reflectance, or the like.

Examples of the metal include copper, iron, nickel, chromium, aluminum,silver, gold and titanium and alloys of those.

Covering Layer 11 c

The wiring substrate 11 has light-reflecting properties, but thelight-reflecting properties may be provided by the wiring 11 a on thewiring substrate 11, or provided by the substrate 11 b made by amaterial that has light-reflecting properties, or provided by a coveringlayer 11 c that has light-reflecting properties and applied on the uppersurface of the wiring substrate 11 in a region other than the wirings tobe electrically connected to the light emitting element. Of those, thelight-reflecting properties is preferably provided by the covering layer11 c that has light-reflecting properties.

Preferable examples of the materials of the covering layer 11 c thatcovers the wiring substrate 11 include a resin material described abovecontaining a light-reflecting material, and an electrically insulatingresist. Examples of the light-reflecting material include white pigmentssuch as titanium oxide, zinc oxide, magnesium oxide, magnesiumcarbonate, magnesium hydroxide, calcium carbonate, calcium hydroxide,calcium silicate, magnesium silicate, barium titanate, barium sulfate,aluminum hydroxide, aluminum oxide, and zirconium oxide. For thelight-reflecting material, one of the above may be used alone or two ormore of the above may be used in combination. The content amount of thelight-reflecting material in a resin material is, in view oflight-reflecting properties and viscosity in a fluid state, or the like,preferably in a range of 10 to 70 wt %, more preferably in a range of 30to 60 wt %.

Light Emitting Element 12 and Light-Reflecting Film 13

Each of the plurality of light emitting elements 12 includes, as shownin FIG. 1C, a sapphire substrate 21 and a semiconductor layeredstructure 22 disposed on a lower surface 21 c of the sapphire substrate21. The lower surface of the semiconductor layered structure 22 isprovided with positive and negative electrodes 23, 24. Alight-reflecting film 13 is disposed on a surface of the sapphiresubstrate 21 that is opposite to the lower surface 21 c of the sapphiresubstrate 21.

The light emitting elements 12 may have a quadrangular shape or a shapeapproximate to a quadrangular shape such as a quadrangular shape withrounded corners, but other appropriate planar shape may be employed.

Sapphire Substrate 21

Each of the sapphire substrates 21 has a lower surface 21 c, a pair offirst lateral surfaces 21 a inclined to the lower surface 21 c, and apair of second lateral surfaces 21 b perpendicular to the lower surface21 c. That is, a cross-section passing the lower surface 21 a and thepair of first lateral surfaces 21 a in each of the sapphire substrates21, one of the pair of first lateral surfaces 21 a forms an acute anglewith the lower surface 21 a and the other of the pair of first lateralsurfaces 21 a forms an obtuse angle with the lower surface 21 a. As longas the lateral surfaces meet the configuration requirements describedabove, for example, a substrate made of hexagonal Al₂O₃, which is asapphire substrate having a principal surface of C-plane, A-plane,R-plane or M-plane, or a plane with an off angle of about ±5° withrespect to one of those planes, can be used. For example, a C-planesapphire or a sapphire having a lower surface 21 c with an off angle of±5° with respect to C-plane can be used. Although the sapphire is notperfectly hexagonal in shape, the sapphire is known to be approximatelyhexagonal (hexagonal system).

When the lower surface 21 c is C-plane (0001), the first lateralsurfaces 21 a may be, for example, (1-100) plane, (01-10) plane, (−1010)plane, or the like, which is, when seen from C-plane in [0001]direction, with an inclination in [−1100] direction, [−1100] direction,or [0-110] direction, respectively. The inclination of the first lateralsurfaces 21 a with respect to the lower surface 21 c may be, forexample, in a range of 1° to 20°, preferably in a range of 2° to 10°. InFIG. 1C, the first lateral surfaces 21 a are substantially in parallelto each other and inclined, for example, at 90±7° to the lower surface21 c. That is, one of the pair of the first lateral surfaces 21 a isinclined at an acute angle (for example, 83°) to the lower surface 21 cand the other of the pair of the first lateral surfaces 21 a is inclinedat an obtuse angle (for example, 97°) to the lower surface 21 c.

Semiconductor Layered Structure 22

Any semiconductor layered structure 22 which can emit light ofpredetermined wavelength can be employed. For example, a light emittingelement for emitting light of blue color or green color, a nitride-basedsemiconductor (In_(x)Al_(y)Ga_(1-x-y)N, 0≤X, 0≤Y, X+Y≤1) can be used.The size and the number of the light emitting elements can be selectedappropriately according to purpose.

The positive and negative electrodes 23 and 24 respectively correspondto anode and cathode, and one or plurality of each may be disposed. InFIG. 1B, each of the light emitting elements 12 is provided with oneeach of the electrodes 23 and 24 respectively corresponding to anode andcathode.

Each of the electrodes 23 and 24 can be formed in an appropriate shapeby using an electrically conductive material.

The positive and negative electrodes 23 and 24 are respectivelyelectrically connected via a bonding member to the wiring 11 a on theupper surface of the wiring substrate 11, as shown in FIG. 1C. That is,each of the light emitting elements 12 is mounted in a flip-chip manner,bridging positive and negative wiring 11 a.

Examples of materials of the bonding member include, bumps made of gold,silver, or copper, a metal paste including a metal powder of silver,gold, or copper and a resin binder, solders such as tin-bismuth-basedsolders, tin-copper-based solders, and brazing materials such aslow-melting-point metals.

Light-Reflecting Layer 13

In each of the light emitting element 12, a light-reflecting film 13 isdisposed on the surface of the sapphire substrate 21 that is opposite tothe lower surface 21 c of the sapphire substrate 21. The reflecting Film13 preferably has an incident angle dependence of reflectance for alight emission wavelength of the light emitting element 12. The opticaltransmittance of the light-reflecting film 13 is dependent on anincident angle, such that as shown in FIG. 2A, substantially no light istransmitted in the normal direction to the upper surface of the lightemitting element 12 but the optical transmittance increases withincreasing inclination angle with respect to the normal direction. Forexample, when the optical transmittance is about 10% to light of anincident angle in a range of −30° to 30°, but the optical transmittancegradually increases to light of incident angle smaller than −30° andrapidly increases to light of incident angle smaller than −50°.Similarly, when the incident angle of light is greater than 30°, theoptical transmittance gradually increases and when the incident angle oflight is greater than 50°, the optical transmittance rapidly increases.That is, the light transmittance of the light-reflecting film 13 tolight from the light emitting element 12 increases as increasing theabsolute value of the incident angle. Accordingly, each of the lightemitting elements 12 having the light-reflecting film 13 exhibitsbatwing light distribution as shown in FIG. 2B in a direction parallelto the second lateral surfaces 21 b of the sapphire substrate 21 (i.e.,a direction of the light emitting elements 12T and 12W parallel to theplane of FIG. 1C) and also exhibits batwing light distribution as shownin FIG. 2C in a direction perpendicular to the second lateral surfaces21 b of the sapphire substrate 21 (i.e., a direction of the lightemitting elements 12Q and 12V parallel to the plane of FIG. 1C).

The batwing light distribution shown in FIG. 2B is asymmetrical withrespect to the viewing angle of zero, due to the inclination of thefirst lateral surfaces 21 a of the sapphire substrate 21. Meanwhile, thebatwing light distribution shown in FIG. 2C is symmetrical with respectto the viewing angle of zero, because the second lateral surfaces 21 bof the sapphire substrate 21 are perpendicular.

A batwing light distribution refers to light distributioncharacteristics having a first intensity peak that is greater intensitythan the intensity at a light distribution angle of 90°, in a firstregion in which a light distribution angle is equal or less than 90°,and a second intensity peak that is greater intensity than the intensityat a light distribution angle of 90°, in a second region in which alight distribution angle is equal or greater than 90°.

With adapting light having such batwing light distributioncharacteristics, the bitch between the light emitting elements in thematrix direction can be increased, and thus the number of the lightemitting elements can be reduced.

The light-reflecting film 13 is provided to reflect at least lightemitted from the light emitting element 12 and made of, for example, ametal material, a resin material containing a white filler, or adielectric multilayer film.

When a dielectric multilayer film is used, a light-reflecting filmexhibiting small absorption of light can be obtained, which facilitatesadjustment of reflectance in a design stage of the film. Further, thereflectance can be accurately adjusted by the incident angle of light.In particular, the batwing light distribution characteristics describedabove can be obtained with good control by increasing the reflectance ina direction perpendicular to the light extracting surface (in otherwords, in an axis direction) and decreasing the reflectance (that is,increasing light transmittance) in a direction that has a large angle tothe optical axis.

Each of the light emitting elements 12 according to the presentembodiment includes the sapphire substrate 21 having the first lateralsurfaces 21 a and the second lateral surfaces 21 b as described above.That is, the light distribution characteristics of emission is affectedby the pair of first lateral surfaces 21 a inclined due to a cleavageplane of the sapphire substrate 21, which produce relatively brighterside and relatively darker side when viewed from above.

The plurality of light emitting elements 12 are, as shown in FIG. 1A,disposed on the upper surface of the wiring substrate 11 in plurality ofrows and/or plurality of columns, in which, a part of the plurality oflight emitting elements in a predetermined region, for example, a regionM in FIG. 1A, are arranged such that one of the pair of first lateralsurfaces 21 a and one of the pair of second lateral surfaces 21 b ofadjacent light emitting elements 12 of the plurality of light emittingelements 12 in at least one of a row direction and a column directionare facing each other. In particular, the light emitting elements 12 inthe predetermined region are preferably arranged such that the firstlateral surface 21 a of the sapphire substrate 12 and the second lateralsurface 21 b of the sapphire substrate 12 of adjacent light emittingelements 12 in the row direction and in the column direction are facingwith each other.

For example, as shown in FIG. 1B and FIG. 1C, the plurality of lightemitting elements 12 are regularly disposed in a matrix direction, inwhich, in a predetermined region M, for example, the first lateralsurface 21 a of the sapphire substrate 21 of the light emitting element12T faces the second lateral surface 21 b of the sapphire substrate 21of the light emitting element 12Q that is adjacent to the light emittingelement 12T in the row direction (X-direction in FIG. 1B). The secondlateral surface 21 b of the sapphire substrate 21 of the light emittingelement 12Q faces the first lateral surface 21 a of the sapphiresubstrate 21 of the light emitting element 12W that is adjacent to thelight emitting element 12Q in the row direction. As shown in FIG. 1C,the pair of first lateral surfaces 21 a of the sapphire substrate 21 ofthe light emitting element 12T are inclined in the opposite direction tothe inclination of the first lateral surfaces 21 a of the sapphiresubstrate 21 of the light emitting element 12W. In other words, as shownin FIG. 1B, the light emitting elements 12 are disposed such that in therow direction along the X direction (from the left side to the rightside in FIG. 1B), one of the pair of first lateral surfaces 21 a ofadjacent light emitting elements 12 are rotated by 90° to the right. Inother words, among every two adjacent light emitting elements 12 in therow direction, the orientation of the light emitting element 12 on theright side is rotated by 90° to the right with respect to theorientation of the light emitting element 12 on the left side.

In a similar manner, the first lateral surface 21 a of the sapphiresubstrate 21 of the light emitting element 12P faces the second lateralsurface 21 b of the sapphire substrate 21 of the light emitting element12R that is adjacent to the light emitting element 12P in the columndirection. The second lateral surface 21 b of sapphire substrate 21 ofthe light emitting element 12R faces the first lateral surface 21 a ofthe sapphire substrate 21 of the light emitting element 12S that isadjacent to the light emitting element 12R in the column direction. Thefirst lateral surface 21 a of the sapphire substrate 21 of the lightemitting element 12S faces the second lateral surface 21 b of thesapphire substrate 21 of the light emitting element 12T that is adjacentto the light emitting element 12S in the column direction. The pair offirst lateral surfaces 21 a of the sapphire substrate 21 of the lightemitting element 12P are inclined in the opposite direction to theinclination of the first lateral surfaces 21 a of the sapphire substrate21 of the light emitting element 12S. In other words, the light emittingelements 12 are disposed such that in the column direction (from the topside to the bottom side in FIG. 1B), one of the pair of first lateralsurfaces 21 a of adjacent light emitting elements 12 are rotated by 90°to the left. In other words, among every two adjacent light emittingelements 12 in the column direction, the orientation of the lightemitting element 12 on the bottom side is rotated by 90° to the leftwith respect to the orientation of the light emitting element 12 on thetop side.

Such arrangement as described above can effectively prevent or reducethe successively continuing brighter pattern and the successivelycontinuing darker pattern that have been occurred when a plurality oflight emitting elements each having a relatively brighter side and arelatively darker side when viewed from above, are disposed regularlyand in the same orientation. Accordingly, uniform intensity distributionof light can be obtained on the light emitting surface and visualrecognition of unevenness in luminance can be avoided or reduced.

In particular, when not only the light emitting elements in thepredetermined region but also all the light emitting elements on thewiring substrate 11 are disposed as described above, more uniformintensity distribution of light can be obtained on the light emittingsurface and visual recognition of unevenness in luminance can be moreeffectively avoided or reduced.

As shown in FIG. 3, the plurality of light emitting elements 12 may bedisposed such that one of the pair of first lateral surfaces 21 a ofadjacent light emitting elements 12 in the row direction (from the leftside to the right side in FIG. 3) are rotated by 90° to the left, andone of the pair of first lateral surfaces 21 a of adjacent lightemitting elements 12 in the column direction (from the top side to thebottom side in FIG. 3) are rotated by 90° to the right. In other words,among every two adjacent light emitting elements 12 in the rowdirection, the orientation of the light emitting element 12 on the rightside is rotated by 90° to the left with respect to the orientation ofthe light emitting element 12 on the left side. Among every two adjacentlight emitting elements 12 in the column direction, the orientation ofthe light emitting element 12 on the bottom side is rotated by 90° tothe right with respect to the orientation of the light emitting element12 on the top side.

Alternatively, as shown in FIG. 4, the plurality of light emittingelements 12 may be disposed such that one of the pair of first lateralsurfaces 21 a of adjacent light emitting elements 12 in the rowdirection (from the left side to the right side in FIG. 4) are rotatedby 45° to the right, and one of the pair of first lateral surfaces 21 aof adjacent light emitting elements 12 in the column direction (from thetop side to the bottom side in FIG. 4) are rotated by 45° to the right.In other words, among every two adjacent light emitting elements 12 inthe row direction, the orientation of the light emitting element 12 onthe right side is rotated by 45° to the right with respect to theorientation of the light emitting element 12 on the left side. Amongevery two adjacent light emitting elements 12 in the column direction,the orientation of the light emitting element 12 on the bottom side isrotated by 90° to the left with respect to the orientation of the lightemitting element 12 on the top side. In a similar manner, the lightemitting elements 12 may be rotated to the right from the top side tothe bottom side in the column direction, and the light emitting elements12 may be rotated to the left from the left side to the right side inthe row direction. As shown in FIG. 4, in every adjacent ones of thelight emitting elements 12 in the row direction and in the columndirection, one of the pair of first lateral surfaces 21 a of one of thelight emitting elements 12 faces one of the pair of second lateralsurfaces 21 b of an adjacent one of the light emitting elements 12,while these facing surfaces are inclined at 45° with respect to eachother.

Further, as shown in FIG. 5, the plurality of light emitting elements 12may be disposed such that in the row direction (from the left side tothe right side in FIG. 5), one of the pair of first lateral surfaces 21a of adjacent light emitting elements 12 are, for example, rotated by45° to the right, and in the column direction, one of the pair of firstlateral surfaces 21 a of adjacent light emitting elements 12 are rotatedby 180°. In other words, among every two adjacent light emittingelements 12 in the row direction, the orientation of the light emittingelement 12 on the right side is rotated by 45° to the right with respectto the orientation of the light emitting element 12 on the left side.Among every two adjacent light emitting elements 12 in the columndirection, the orientation of the light emitting element 12 on thebottom side is rotated by 180° with respect to the orientation of thelight emitting element 12 on the top side. In this case shown in FIG. 5,the first lateral surface 21 a of the light emitting elements 12 and thesecond lateral surface 21 b of adjacent light emitting elements 12 arefacing each other only in the row direction.

Although not shown in FIG. 4 and FIG. 5, the wiring 11 a of the wiringsubstrate 11 can be appropriately disposed on the upper surface, on thelower surface, or inside of the wiring substrate 11, according to thearrangement of the light emitting element 12 as described.

Other than a rotation of the light emitting elements 12 at 45°, 90°,180° or the like, a rotation of any appropriate angle can be applied toarrange the light emitting elements regularly or randomly.

Accordingly, the successively continuing brighter pattern and thesuccessively continuing darker pattern can be efficiently avoided orreduced, and uniform intensity distribution of light can be obtained onthe light emitting surface and visual recognition of unevenness inluminance can be avoided.

Underfill 15

Each of the light emitting elements 12 mounted on the upper surface ofthe wiring substrate 11 are preferably provided with an underfill 15disposed around each of the light emitting elements 12 and/or betweeneach of the light emitting elements 12 and corresponding portions of thewiring substrate 11. The underfill 15 may contain a filler, a pigment,or/and light-reflecting material etc., to obtain the thermal expansioncoefficient closer to the thermal expansion coefficient of the lightemitting elements 12, to prevent or reduce scattering and reflection oflight from the light emitting elements 12 at the wiring substrate 11,and to extract light from the light emitting elements 12 efficiently tothe opposite side of the wiring substrate 11.

The underfill 15 can be made of a material resistance to deteriorationdue to light from the light emitting elements 12. Examples of thematerials of the underfill 15 include an epoxy resin, a silicone resin,a modified silicone resin, a urethane resin, an oxetane resin, anacrylic resin, a poly carbonate resin and a polyimide resin. With theuse of the filler or pigment made of a material that absorbs emissionwavelength of light, light is less likely reflected and scattering oflight can be reduced or prevented. In order to prevent or reducedeterioration due to light, an inorganic compound is preferably used forthe light-absorption material.

Sealing Member 16

Each of the light emitting elements 12 mounted on the upper surface ofthe wiring substrate 11 are preferably sealed with a sealing member 16.

The sealing member 16 may be formed with a light-transmissive material,examples thereof include, an epoxy resin, a silicone resin, a mixedresin of those, and glass. Of those, a silicone resin is preferably usedin view of light-resisting properties and the ease of molding.

The sealing member 16 may be formed in a dome shape, a bowl shape, orthe like, or such a shape with a depression corresponding to a center ofa light emitting element 12. The sealing member 16 may also formed in alens shape that can produce a batwing light distribution. The shape ofthe sealing member 16 on the wiring substrate 11 may be circular, orhexagonal or octagonal, or the like.

The sealing member 16 can be formed to cover the corresponding one ormore light emitting elements 12 by using compression molding, injectionmolding, or the like. Also, the shape of the sealing member 16 can becontrolled by using the surface tension of the material of the sealingmember, in which the viscosity of the material of the sealing member 16is optimized and applied it on the light emitting elements 12 in dropsor by drawing.

Light-Diffusing Member 14

The light diffusing member 14 is disposed above the plurality of lightemitting elements 12. The light diffusing member 14 may be provided foreach group of light emitting elements 12, or a single light diffusingmember 14 may be provided above all the light emitting elements 12 inthe light emitting device. The light diffusing member 14 is preferablydisposed above substantially in parallel to the upper surfaces of thelight emitting elements 12. With the use of the light diffusing member14 described above, light emitted from the plurality of light emittingelements 12 can be transmitted while further diffusing, and thusunevenness in luminance can be reduced.

In particular, when the light diffusing member 14 is used with the lightemitting elements 12 each having the sapphire substrate that has thefast lateral surfaces 21 a described above, contrast of relativelybrighter sides and relatively darker sides of the light emittingelements when viewed from above tend to be increased. However, accordingto the present embodiment, the plurality of light emitting elements 12are disposed in a matrix in which the first lateral surface 21 a and thesecond lateral surface 21 b of each adjacent two light emitting elements12 face with each other, which offsets the successively continuingbrighter pattern and the successively continuing darker pattern, andthus occurrence of unevenness in luminance can be efficiently avoided orreduced.

Examples of the materials of the light diffusing member 14 includematerials of smaller absorption to visible light such as polycarbonateresins, polystyrene resins, acrylic resins, and polyethylene resins. Inorder to diffuse light, materials having different refractive index maybe contained in the light diffusing member 14, or the surface may betextured to scatter light, or other appropriate methods may be employed.

In the light emitting device according to the present embodiment, awavelength converting member may be disposed at front side or backsideof the light diffusing member 14 with respect to light emitted from thelight emitting elements 12. The wavelength converting member may be, forexample, made of a light-transmissive resin containing one or more knownfluorescent materials, or made of a sintered fluorescent material.

As described above, when a plurality of light emitting elements 12 eachhaving a pair of first lateral surfaces 21 a inclined to the lowersurface 21 c of the sapphire substrate 21 and a pair of second lateralsurfaces 21 b perpendicular to the lower surface 21 c of the sapphiresubstrate 21 are disposed in a matrix of rows and columns on thelight-reflecting substrate, and the light-reflecting film 13 and lightdiffusing member 14 are used in combination, occurrence of successivelycontinuing brighter pattern and successively continuing darker patterncan be efficiently avoided or reduced by a simple method of changing theorientation of the light emitting elements in the matrix direction.Accordingly, uniform intensity distribution of light can be obtained onthe light emitting surface and visual recognition of unevenness inluminance can be avoided.

The light emitting device according to the present disclosure can besuitably used for various display devices, luminaires, displays,backlight light sources of liquid crystal displays, further, for imagereading apparatus for photocopiers, scanners, or the like, projectors,laser display devices, endoscopes, vehicular headlights, bar codescanners, or the like.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

What is claimed is:
 1. A light emitting device comprising: a wiringsubstrate having light-reflecting properties, the wiring substrateincluding a wiring; a plurality of light emitting elements mounted in amatrix of rows and columns on an upper surface of the wiring substrate,the light emitting elements each including a sapphire substrate having alower surface, a pair of first lateral surfaces slanted with respect tothe lower surface, and a pair of second lateral surfaces perpendicularto the lower surface, with the pair of first lateral surfaces has anacute angle lateral surface that forms an acute angle with the lowersurface and an obtuse angle lateral surface that forms an obtuse anglewith the lower surface in a cross-section passing through the lowersurface and the pair of first lateral surfaces, and a semiconductorlayered structure disposed on the lower surface of the sapphiresubstrate; a plurality of light-reflecting films respectively disposedon upper surfaces of the light emitting elements; and a light diffusingmember disposed above the light emitting elements; wherein at least agroup of the light emitting elements disposed in a predetermined regionincludes a first light emitting element, a second light emitting elementand a third light emitting element arranged such that, the first lightemitting element, the second light emitting element and the third lightemitting element are aligned along one of a row direction and a columndirection of the matrix with the second light emitting element beingdisposed between the first light emitting element and the third lightemitting element, one of the acute angle lateral surface and the obtuseangle lateral surface of the first light emitting element faces one ofthe pair of second lateral surfaces of the second light emittingelement, and one of the acute angle lateral surface and the obtuse anglelateral surface of the third light emitting element faces the other ofthe pair of second lateral surfaces of the second light emittingelement.
 2. The light emitting device according to claim 1, wherein thegroup of the light emitting elements are arranged such that, in everyadjacent ones of the light emitting elements in both the row directionand the column direction of the matrix, one of the pair of first lateralsurfaces of one of the light emitting elements faces one of the pair ofsecond lateral surfaces of an adjacent one of the light emittingelements.
 3. The light emitting device according to claim 1, wherein allof the light emitting elements are arranged such that, in every adjacentones of the light emitting elements in at least one of the row directionand the column direction of the matrix, one of the pair of first lateralsurfaces of one of the light emitting elements faces one of the pair ofsecond lateral surfaces of an adjacent one of the light emittingelements.
 4. The light emitting device according to claim 1, wherein thelight-reflecting films are respectively disposed on the upper surfacesof the light emitting elements so that each of the light emittingelements provided with a corresponding one of the light-reflecting filmshas batwing light distribution characteristics.
 5. The light emittingdevice according to claim 1, wherein each of the light emitting elementshas a pair of electrodes at a lower surface side of the semiconductorlayered structure with the pair of electrodes being connected to thewiring so that each of the light emitting elements is mounted on thewiring substrate in a flip-chip manner.
 6. The light emitting deviceaccording to claim 1, wherein the light emitting device is a direct-litbacklight light source.
 7. The light emitting device according to claim1, wherein the group of the light emitting elements are arranged suchthat, in every adjacent ones of the light emitting elements in at leastone of the row direction and the column direction of the matrix, thepair of first lateral surfaces of the one of the light emitting elementsis substantially parallel to the pair of second lateral surfaces of theadjacent one of the light emitting elements in a plan view.
 8. The lightemitting device according to claim 2, wherein the group of the lightemitting elements are arranged such that, in every adjacent ones of thelight emitting elements in both the row direction and the columndirection of the matrix, the pair of first lateral surfaces of the oneof the light emitting elements is substantially parallel to the pair ofsecond lateral surfaces of the adjacent one of the light emittingelements in a plan view.
 9. The light emitting device according to claim1, wherein the group of the light emitting elements are arranged suchthat, in every adjacent ones of the light emitting elements in at leastone of the row direction and the column direction of the matrix, thepair of first lateral surfaces of the one of the light emitting elementsis slanted with respect to the pair of second lateral surfaces of theadjacent one of the light emitting elements in a plan view.
 10. Thelight emitting device according to claim 2, wherein the group of thelight emitting elements are arranged such that, in every adjacent onesof the light emitting elements in both the row direction and the columndirection of the matrix, the pair of first lateral surfaces of the oneof the light emitting elements is slanted with respect to the pair ofsecond lateral surfaces of the adjacent one of the light emittingelements in a plan view.
 11. The light emitting device according toclaim 1, wherein the obtuse angle lateral surface of the first lightemitting element faces the one of the pair of second lateral surfaces ofthe second light emitting element, and the obtuse angle lateral surfaceof the third light emitting element faces the other of the pair ofsecond lateral surfaces of the second light emitting element.